JP2015161851A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to reduce or prevent cracks or damage to a lateral end of a fixing belt when a ring member in contact with an end of the fixing belt is used.SOLUTION: A fixing apparatus includes: a rotatable endless fixing belt 6A1; an opposite rotating body 6B1 which forms a nip part N, in contact with the fixing belt 6A1; a ring member 60 which faces a lateral end of the fixing belt 6A1 and rotates integrally with the fixing belt 6A1; a support flange section 50 which forms a gap larger than a thickness of the ring member 60, in a lateral direction, with an end of the fixing belt 6A1 which occupies a lateral prescribed position; and a movable positioning mechanism 70 which positions the ring member 60 with respect to the support flange section 50 in the lateral direction, to position the lateral end in the lateral direction, and positions the fixing belt 6A1 in the prescribed position.

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly to a member positioning mechanism used for fixing.

  As is well known, in an electrophotographic image forming apparatus, an electrostatic latent image formed on a photoreceptor, which is a latent image carrier, is subjected to visible image processing with toner, and the toner image is a recording medium such as recording paper. A copy output is obtained by being transferred to the image and fixed.

A heat roller fixing method is well known as a fixing method used in an image forming apparatus.
In this system, a fixing roller and a pressure roller that are in contact with each other across the conveyance path of the recording paper are used, and pressure is applied by the clamping action between the heat from the heat source provided in the fixing roller and the pressure roller. The toner image is fixed.
A belt fixing system is also known in which a fixing belt serving as a good heat conductor instead of the fixing roller, a pressure roller, a roller equipped with the belt, and a heating source for the belt are provided (for example, Patent Document 1). Further, a film fixing method in which a thin film is heated with a ceramic heater instead of a fixing belt, or an electromagnetic induction heating fixing method for increasing heat generation efficiency is known (for example, Patent Document 2).
In recent years, it has been desired for the fixing device to further shorten the warm-up time (the time required from a normal temperature state to a predetermined printable temperature (reload temperature) such as when the power is turned on). In addition to this, it has also been desired to shorten the first print time (the time from when a print request is received to when the print operation is performed and the paper discharge is completed).

Therefore, the metal heat conductor is composed of an endless belt, and is not indirectly heated, but is provided with a nip forming member that directly heats the endless belt and forms the nip width of the fixing belt with respect to the pressure roller. A configuration has been proposed by the present applicant (for example, Patent Document 3).
In the above configuration, quick start-up (QSU) is possible by directly heating an endless belt made of a thin metal. Further, unlike the case where a heating roller is used by providing a nip forming member, the nip width can be secured and the fixing efficiency can be prevented from being lowered even when the apparatus is downsized.

Endless belts have been developed in addition to metal. This is based on, for example, polyamide.
The endless belt using such a material provides the following advantages.
In other words, since the heat capacity is low, it is possible to aim for energy savings by further reducing the heat capacity, and because the flexibility is high, it is advantageous for the separation between the paper tip and the belt, and the thermal expansion seen in the metal belt during an emergency stop There is a high possibility that the shape will be restored even if the indentation deformation occurs.

By the way, when using a belt such as a fixing device (for example, Patent Document 3), the belt is wide due to an outer diameter error of a roller around which the belt is wound or a case where the rollers are not parallel to each other. The belt may be shifted, which is a phenomenon that shifts to one side in the direction.
When this phenomenon occurs, for example, in the case of a fixing belt, the area to be heat-fixed may deviate from a predetermined area, and the fixing operation may not be performed on the recording paper area that requires fixing.

As a technique for suppressing the deviation of the belt, for example, Patent Document 4 discloses a technique including a configuration capable of positioning the belt edge.
In the above technique, a ring member having an end face capable of abutting on the belt end is opposed to the belt end, and the ring member is inclined in the axial direction by receiving pressure when the belt comes in contact with the side of the belt. It is used.
In this configuration, when the guide member is tilted in the axial direction, the reaction force acting on the belt end is weakened by utilizing the reduced component force in the contact direction obtained from the tilt of the ring member. With this, the belt can be positioned.

In a conventional fixing device using an endless belt, the nip pressure at the fixing nip portion is a relatively high pressure of 50 to 200 KPa. However, the fixing efficiency obtained when a known technique (for example, Patent Document 3) is used. Improvement can reduce the nip pressure.
When the nip pressure can be lowered, there is an advantage that the rigidity of the mechanism part such as a nip forming member can be lowered. On the other hand, when a nonmetallic endless belt is mounted for such a configuration, the belt There is a risk that mechanical deterioration is likely to occur. In other words, when the belt end face is rubbed against the ring member or the flange, mechanical deterioration such as wear and cracks with time tends to occur.

The wear of the belt end face depends on the biasing force of the belt, the mechanical strength of the belt end face, and the contact time thereof. However, since the mechanical strength of the non-metallic belt is low, there is a prisoner of shortening the wear resistance time.
When the belt end surface comes into contact with the ring member or the flange, the state of being pressed by the nip pressure described above continues, so that the members are not separated from each other, and the load acting on the sleeve end surface is unlikely to decrease. For this reason, wear due to continuous contact easily proceeds.

Regarding the damage to the belt end surface, when a ring member having a known configuration (for example, Patent Document 4) is used, the belt end surface remains in contact if the ring member is kept stationary to position the belt end surface. Therefore, wear progresses.
As described above, when the end face of the belt is worn or cracked due to an impact at the time of collision, the end face positioning accuracy and mechanical durability are lowered due to a change in dimensions in the width direction of the endless belt.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus that reduce or prevent cracking and breakage of the end portion of the fixing belt when a ring member that contacts the end portion of the fixing belt is used.

  To achieve this object, the present invention includes a rotatable endless fixing belt, a counter rotating body that forms a nip portion between the fixing belt and the fixing belt in contact with the fixing belt, and fixing. A ring member facing the end in the width direction of the belt and rotatable integrally with the fixing belt; and the ring between the end in the width direction with the fixing belt occupying a specified position in the width direction. A support flange portion that forms an interval larger than the thickness of the member; and the end portion is positioned in the width direction by positioning the ring member with respect to the support flange portion in the width direction, and the fixing belt is moved to the specified position. A fixing device having a movable positioning mechanism.

  According to the present invention, it is possible to obtain a fixing device capable of reducing or preventing deterioration of the end surface of the fixing belt even when the end surface of the fixing belt hits the ring member due to the deviation of the fixing belt and correcting the fixing belt to a specified position. Can do.

FIG. 3 is a schematic diagram for explaining a configuration of an example of an image forming apparatus including an example of a fixing device to which the present invention is applied. FIG. 2 is a schematic diagram for explaining a configuration of a fixing device illustrated in FIG. 1. FIG. 3 is a diagram for explaining a configuration of members used in the fixing device shown in FIG. It is a figure for demonstrating the structure used for the structure shown in FIG. It is a figure for demonstrating the modification of the structure shown in FIG. It is a figure for demonstrating the state at the time of operation | movement of the landing apparatus of the structure shown in FIG. FIG. 5 is a diagram for explaining a state in which the counter rotator is separated from the flexible fixing belt when the configuration illustrated in FIG. 4 is not passed. FIG. 5 is a diagram for explaining a state in which the counter rotator is in contact with a flexible fixing belt in the paper preparation state of the configuration illustrated in FIG. 4.

Hereinafter, an example of an embodiment for carrying out the present invention will be described with reference to the drawings.
1A shows a state in which an opening / closing cover 100B as an opening / closing member provided in a part of the casing 100A of the image forming apparatus 100 is closed, and FIG. 1B shows a state in which the opening / closing cover 100B is opened. It shows the state.

As shown in FIG. 1, in the image forming apparatus 100, an opening / closing cover 100B is provided in a part of a casing 100A constituting the apparatus main body so as to be opened and closed.
Inside the housing 100A, image forming stations 101Y, 101M, 101C, and 101K are provided as image forming units for forming images of a plurality of colors. These image forming stations 101Y, 101M, 101C, and 101K are juxtaposed along the extended surface of the intermediate transfer belt 102A provided in the transfer device 102 disposed below them.

Each of the image forming stations 101Y, 101M, 101C, and 101K has the same configuration that is used except that the colors to be formed are different. Therefore, the configuration for the black image forming station 101K will now be described. .
The image forming station 101K is provided with a rotatable drum-shaped photosensitive member 1K.
Around the photoreceptor 1K, there are provided a charging device 1K1 for performing image forming processing at the time of rotation, a writing device (indicated by a symbol L attached to the optical path for convenience), a developing device 1K2, and a cleaning device (not shown). The photosensitive body 1K shown in FIG. 1 has a clockwise rotation direction.
The photoreceptor 1 </ b> K is uniformly charged by the charging device 1 </ b> K <b> 1 in the process of rotating, and then an electrostatic latent image is formed by the writing device L. The electrostatic latent image is subjected to visible image processing with a developer supplied from the developing device 1K2, and then electrostatically transferred to the transfer belt 102A by the primary transfer device 102B.
The images formed in the image forming stations 101Y, 101M, and 101C other than black are subjected to visible image processing similar to the processing in the black image forming station 101K, and then sequentially transferred to the transfer belt 102A.
After the image transfer to the transfer belt 102A at the image forming station 101K, the photosensitive member 101K is cleaned by removing untransferred toner by a cleaning device (not shown). In the image forming stations 101Y, 101M, and 101C other than black, processing by the cleaning device is similarly performed.
Through the above steps, the superimposed image of each color is carried on the transfer belt 102A.

The housing 100A of the image forming apparatus 100 is provided with a paper feeding device 2 for feeding the recording paper P onto which the image carried on the transfer belt 102A is transferred.
The paper feeding device 2 is provided with a paper feeding cassette 2 </ b> A containing the recording paper P and a feeding roller 2 </ b> B. The recording paper P separated by a separation mechanism (not shown) is fed toward the registration roller pair 4. The
The recording paper P fed out from the paper feeding device 2 is set at a registration timing by a registration roller pair 4 disposed in the housing 100A, and is directed to a secondary transfer position provided with the secondary transfer device 5. It is paid out.
A conveyance path for the recording paper P is formed between the registration roller pair 4 and the secondary transfer position, and the conveyance roller pair 3 capable of nipping and conveying the recording paper P together with the registration roller pair 4 is formed in the conveyance path. Is provided.

In the configuration shown in FIG. 1, one of the rollers constituting the registration roller pair 4 and the conveyance roller pair 3 capable of nipping and conveying the recording paper P is disposed on the housing 100A, and the other is disposed on the opening / closing cover 100B side. .
Thus, when the opening / closing cover 100B is opened, the conveyance path of the recording paper P on which the registration roller pair 4 and the conveyance roller pair 3 are arranged can be opened.
The opening / closing cover 100B includes a pressure roller 6B1 as a counter rotating body capable of forming a nip portion facing a fixing belt 6A1 provided in the fixing device 6 described later, one of the roller pairs 3 and 4, and a secondary roller. The transfer devices 5 are respectively arranged.

The secondary transfer device 5 that collectively transfers the image carried on the transfer belt 102A to the recording paper P fed out from the paper supply device 2 uses a roller facing the roller around which the transfer belt 102A is wound. It has been.
The recording paper P that has reached the secondary transfer position is transferred with the image carried on the transfer belt 102 </ b> A by the transfer bias applied to the secondary transfer device 5.
The recording sheet P, which has been transferred at the secondary transfer position, is conveyed toward the fixing device 6 to fix the image, and is discharged by the discharge roller pair 7 toward the discharge tray 100C provided on the upper surface of the housing 100A. Discharged.

The fixing device 6 includes a nip portion N between the fixing heating unit 6A having an endless and flexible rotatable fixing belt 6A1 and the fixing belt 6A1 in contact with the fixing belt 6A1. A pressure unit 6B including a pressure roller 6B1 to be formed is used.
The pressure roller 6B1 is a member capable of nipping and conveying the recording paper P when the nip portion N is formed by contacting the fixing belt 6A1.
The configuration of the fixing device 6 will be described later in detail with reference to FIG.

As shown in FIG. 1, the fixing heating unit 6A provided with members other than the pressure roller 6B1 of the fixing device 6 is disposed on the housing 100A side. Moreover, the pressure part 6B provided with the pressure roller 6B1 as a main part is provided on the opening / closing cover 100B side described above.
For this reason, when the opening / closing cover 100B is opened with respect to the housing 100A using a shaft (not shown) provided in the housing 100A as a fulcrum, the inside of the image forming apparatus 100 is opened as shown in FIG. At the same time, the pressure roller 6B1 is separated from the fixing belt 6A1. As a result, the conveyance path up to the fixing device 6 is exposed to the outside with the position of the registration roller pair 4 after feeding out the recording paper P as the conveyance path start point. The opening / closing cover 100B is provided with a hook member 100B1 that can be engaged with the engaging portion of the housing 100A so that the opening / closing cover 100B can be kept closed.

As shown in FIG. 2, a fixing belt 6A of the fixing device 6 directly heats a fixing belt 6A1, a nip forming member 6A3 supported by a supporting member 6A2 located inside the fixing belt 6A1, and a fixing belt 6A1. A plurality of heating sources 6A4 are provided.
A pressure roller 6B1 including a core metal 6B10, an elastic layer 6B11, and a release layer 6B12 is used for the pressure unit 6B.
The elastic layer 6B11 is disposed on the surface of the core metal 6B1A, and foamed silicone rubber, silicone rubber, fluorine rubber, or the like is used.
The release layer 6B12 is provided on the surface of the elastic layer 6B11, and PFA, PTFE, or the like is used. The pressure roller 6B1 is provided on the fixing heating unit 6A side by a pressing spring as an elastic body indicated by reference numeral 84 in FIG. The belt is biased toward the fixing belt 6A1 and presses the fixing belt 6A1 toward the nip forming member 6A3.
At the place where the pressure roller 6B1 and the fixing belt 6A1 are in contact, the elastic layer 6B11 is crushed to form a nip portion N having a predetermined width.
In FIG. 2, reference numeral 6A5 denotes a reflecting member that reflects radiant heat from the heating source 6A4 toward the fixing belt 6A1.

  FIG. 3 shows a support mechanism for the fixing belt 6A1 used in the fixing device 6 shown in FIG. 2, wherein (A) is a perspective view, (B) is a plan view, and (C) is a rotation of the fixing belt 6A1. Each state viewed from the axial direction is shown. 3 (A) to 3 (C), only the configuration of one end is shown, but the opposite end also has the same configuration. Only the configuration of the end will be described.

As shown in FIG. 3A or 3B, a belt holding member 40 that guides the fixing belt 6A1 toward the nip forming member 6A3 is inserted into the end portion in the width direction of the fixing belt 6A1.
Although not shown in detail in the belt holding member 40, as shown in FIG. 3 (C), a portion where the nip forming member 6A3 is arranged in the circumferential direction is opened and the cross-sectional shape is substantially C-shaped. is there. At both ends in the axial direction of the belt holding member 40, both ends in the axial direction of the support member 6A2 that supports the nip forming member 6A3 are fitted.
As shown in FIG. 3C, a nip forming member 6A3 is arranged and attached to the position where the belt holding member 40 is opened.

As shown in FIG. 3B, the belt holding member 40 is supported at both ends in the axial direction by support flange portions 50.
The support flange portion 50 is configured by a disk-shaped block body having a boss portion 50A, a base portion is supported by a side wall 100A1 on the housing 100A side, and the boss portion 50A is fitted into both axial ends of the belt holding member 40. .
The support flange portion 50, specifically, the boss portion 50A is formed between the ring member 60 described later between the fixing belt 6A1 and the surface of the end portion in the width direction of the fixing belt 6A1 in a state where the fixing belt 6A1 occupies a specified position in the width direction. An interval larger than the thickness is formed.
As shown in FIG. 3B, the boss portion 50A is formed with a step portion 50B at a part of the portion into which the belt holding member 40 is fitted. The step portion 50B is formed by a sloped surface facing the widthwise end surface of the fixing belt 6A1. The position of the stepped portion 50B in the circumferential direction of the boss portion 50A is opposed to a position where a swing end 71A (see FIG. 4) of a guide member 71 described later can advance and retreat.

Between the stepped portion 50B and the surface of the end portion in the width direction of the fixing belt 6A1, a ring member 60 serving as a belt protection member that faces the end portion in the width direction of the fixing belt 6A1 and can be rotated when contacted. Is fitted so that it can rotate independently.
The ring member 60 is inserted through both axial ends of the belt holding member 40 and is rotatably supported.
The ring member 60 is a member that prevents the surface of the end portion in the width direction of the fixing belt 6A1 from directly colliding with the end surface of the boss portion 50A of the support flange portion 50.
For this reason, the fixing belt 6 </ b> A <b> 1 is prevented from directly colliding with the end surface of the boss part 50 </ b> A by coming into contact with the ring member 60 when a deviation occurs in the axial direction, and moves around while contacting the ring member 60. be able to.

  Since the ring member 60 can be rotated while being in contact with the fixing belt 6A1, the opposing surface to the fixing belt 6A1 and the opposing surface to the support flange portion 50 on the fixed side are respectively surfaces made of a low friction coefficient material. Has been. As a result, the frictional resistance with the fixing belt 6A1 and the frictional resistance with the boss portion 50A are reduced.

The fixing device 6 having the above configuration includes a movable positioning mechanism 70 for repositioning the fixing belt 6A1 to a specified position in a separated state in which the pressure roller 6B1 and the fixing belt 6A1 are separated from each other when paper is not passed. Is provided.
The movable positioning mechanism 70 is a mechanism for positioning the ring member 60 in the width direction of the fixing belt 6A1 and positioning the fixing belt 6A1 at a specified position. As shown in FIG. The guide member 71 is provided.
The guide member 71 is a lever member capable of seesaw motion by swinging at both ends in the extending direction with the support shaft 72 as a fulcrum. As shown in FIG. 6, the support flange portion 50 and the ring member 60 in the width direction of the fixing belt 6A1. A swing end 71 </ b> A that can be advanced and retracted is provided in the gap. As described above, the swingable end 71A that can be advanced and retracted is disposed at a position facing the stepped portion 50B so that it can advance and retract with respect to the stepped portion 50B. The step portion 50B shown in FIG. 6 is formed of a tapered portion 50B1 that approximates this.

As shown in FIG. 6, the guide member 71 has a thickness parallel to the width direction of the fixing belt 6A1, and when the end surface of the guide member 71 in the width direction comes into contact with the support flange portion 50 and the ring member 60, the fixing is performed. The belt 6A1 corresponds to the thickness that occupies the specified position.
For this reason, when the guide member 71 moves out of the gap and the pressure roller 6B1 comes into contact with the fixing belt 6A1, the position of the surface of the end portion in the width direction of the fixing belt 6A1 is positioned at the specified position. become.

Returning to FIG. 4, the guide member 71 is pulled by an elastic body 73 such as a coil spring attached to the swing end 71 </ b> A (in the direction indicated by an arrow F in the figure), thereby turning clockwise in FIG. 4. Is granted. The elastic body 73 is not limited to a coil spring, and a torsion spring, a string spring, or the like can also be used.
In the clockwise turning behavior, the swinging end 71A of the guide member 71 is made to enter the gap located at the facing portion between the ring member 60 and the stepped portion 50B of the support flange portion 50 (see FIG. 3B). work.

As shown in FIG. 4, the pressure roller 6B1 facing the fixing belt 6A1 can be brought into contact with and separated from the fixing belt 6A1 by the contact / separation mechanism 80.
The contact / separation mechanism 80 includes a swing lever 81 that is a lever member that is swingably supported by a support shaft 81A.
The swing lever 81 is formed with a recess 81B that contacts the rotation shaft 82 of the pressure roller 6B1 on the way from the swing base end side to the swing end, and the recess 81B contacts the rotation shaft 82 at the swing end. One end in the extending direction of the elastic body 83 that is biased in the direction to be moved is disposed.
The rotating shaft 82 of the pressure roller 6B1 is provided with a receiving portion 85 that latches one end in the extending direction of the elastic body 84 that urges the pressure roller 6B1 toward the fixing belt 6A1.

The guide member 71 and the swinging lever 81 are provided on the swinging end side, and are converted into an operation for contacting and separating the rotational operation to make the fixing belt 6A1 and the pressure roller 6B1 come into contact with and separated from each other. 90 is provided.
The eccentric cam 90 is a member having a substantially rice pad-shaped cam profile that is rotatably supported by the support shaft 90A. By setting the rotational phase of 180, the eccentric cam 90 swings between the guide member 71 and the swing lever 81. Control the movement.
Therefore, when the pressure roller 6B1 is separated from the fixing belt 6A1 due to the posture of the eccentric cam 90, the guide member 71 moves between the support flange portion 50 and the ring member 60 in conjunction with the posture of the eccentric cam 90. The swinging end 71A is entered in between.

Note that the guide member 71 and the swing lever 81 are not limited to the configuration interlocked with the single eccentric cam 90. For example, as shown in FIG. 5, it is possible to provide the guide member 71 and the swing lever 81 with a mechanism for swinging independently. That is, a plunger 91 having an actuator that can advance and retreat is used for the guide member 71, and an eccentric cam 92 is used for the swing lever 81. Although not shown in FIG. 5, the elastic body 84 and the receiving portion 85 shown in FIG. 4 are provided on the opposite side of the position shown in FIG. 4 with the rotation center of the rotation shaft 82 of the pressure roller 6B1 interposed therebetween. Thus, the urging force that the pressure roller 6B1 is separated from the fixing belt 6A1 is applied. Further, in FIG. 5, reference numeral 86 denotes an elastic body that imparts the habit of bringing the swing lever 81 into contact with the eccentric cam 92.
In this configuration, the pressure roller 6B1 contacts and separates from the fixing belt 6A1 according to the attitude of the eccentric cam 92, and the plunger 91 advances and retracts in accordance with the contact and separation timing of the pressure roller 6B1, thereby preventing the gap described above. The advance / retreat operation of the guide member 71 is performed.

In the movable positioning mechanism 70 having the above configuration, the swinging end 71A of the guide member 71 is out of the gap when the sheet is passed through the fixing device 6, and the swinging end 71A enters the gap when the sheet is not passing. .
If the deviation of the fixing belt 6A1 occurs, when the swing end 71A enters, the ring member 60 is pushed and moved to correct the deviation of the fixing belt 6A1, and the surface of the end portion in the width direction of the fixing belt 6A1. Return to the original position (specified position).
As shown in FIG. 6, when the fixing belt 6A1 is displaced while the pressure roller 6B1 is in contact with the fixing belt 6A1, the surface of the end portion in the width direction of the fixing belt 6A1 contacts the ring member 60. . Between the boss portion 50 </ b> A and the belt holding member 40, a gap having a gap larger than the thickness of the ring member 60 is provided between the boss portion 50 </ b> A and the ring member 60. You can move freely.

For this reason, when the surface of the end portion in the width direction of the fixing belt 6A1 contacts and is pressed, the ring member 60 moves to a position where it abuts on the end surface of the boss portion 50A having the stepped portion 50B, and further moves in the axial direction. Is prevented from doing.
The ring member 60 that is prevented from moving in the axial direction is in contact with the end surface of the fixing belt 6A1 in the width direction and the end surface of the boss portion 50A. Since the surface of the ring member 60 facing the fixing belt 6A1 and the boss portion 50A is made of a low friction coefficient material, the rotational resistance in a state where the ring member 60 is in contact with the fixing belt 6A1 and / or the boss portion 50A is small. Therefore, there is an advantage that cracks and breakage of the end portion of the fixing belt 6A1 are reduced or prevented. In order to obtain this advantage, it is only necessary that at least the end surface of the ring member 60 on the fixing belt 6A1 side is made of a low friction coefficient material.

Moreover, the fixing belt 6A1 is prevented from colliding with the boss portion 50A of the support flange portion 50 by the ring member 60, and the force generated at the time of the collision with the ring member 60 is spent on the axial movement of the ring member 60, so The acting reaction force is relaxed.
This prevents the end face in the width direction of the fixing belt 6A1 from being cracked or damaged by the collision force.

The operation of returning the fixing belt 6A1 that has been displaced and pushed the ring member 60 back to the original specified position is executed when the pressure roller 6B1 is not spaced from the fixing belt 6A.
This time corresponds to the time when the open cover 100B is opened and the pressure roller 6B1 is separated from the fixing belt 6A1, or the next time. That is, it can be said that the eccentric cam 90 or the eccentric cam 92 described later is electrically rotated without opening the housing 100A, and is in a separated state by this rotational drive.
As shown in FIG. 7, when the pressure roller 6B1 is separated from the fixing belt 6A1, the swing end 71A of the guide member 71 is separated from the stepped portion 50B along the tapered portion 50B1 formed in the stepped portion 50B. It enters into the gap between the ring member 60 facing this. In FIG. 7, an arrow S indicates a direction in which the swing end 71 </ b> A of the guide member 71 enters the gap.
When the swing end 71A of the guide member 71 enters the gap, the eccentric cam 90 shown in FIG. 4 rotates 180 degrees from the initial position (the position indicated by the solid line) (the position indicated by the two-dot chain line), or The plunger 91 shown in FIG. 5 advances the actuator to swing the swing end 71A.

  The pressure roller 6B1 is set to be separated by the rotational phase change of the eccentric cams 90 and 92 shown in FIGS. In FIG. 7, the arrow R indicates the direction in which the pressure roller 6B1 is separated from the fixing belt 6A1.

  When the sheet is not fed, the pressure roller 6B1 is separated from the fixing belt 6A1, and an environment in which a resistance force to move the fixing belt 6A1 in the width direction does not act. For this reason, when the swing end 71A of the guide member 71 enters the gap, the ring member 60 can be moved in the width direction of the fixing belt 6A1 with a small force. Thereby, the surface of the end portion in the width direction of the fixing belt 6A1 pushed and moved by the ring member 60 is returned to the specified position and positioned.

  After the ring member 60 is pushed and moved to return the fixing belt 6A1 to the specified position and positioned, the guide member 71 moves out of the gap. The withdrawal operation of the guide member 71 can be performed by changing the rotational phase from the position when the eccentric cam 90 shown in FIG. 4 enters (a position indicated by a two-dot chain line) to an initial position (a position indicated by a solid line).

  The pressure roller 6B1 is set in a state of contact by changing the rotational phase of the eccentric cams 90 and 92 shown in FIGS.

As shown in FIG. 8, when the swinging end 71A of the guide member 71 is retracted from the gap (movement in the direction indicated by the arrow S ′ in FIG. 8), the end of the fixing belt 6A1 in the width direction as described in FIG. The ring member 60 is positioned at a position where the surface of the part is returned to the specified position.
The ring member 60 is in a state where it can freely move in the axial direction when the swinging end 71A is retracted by returning the fixing belt 6A1 to the specified position. Therefore, after that, until the fixing belt 6A1 is displaced and pushed, there are few opportunities for continuous rubbing with the fixing belt 6A1.
As a result, since the fixing belt 6A1 returned to the specified position is prevented from continuously rubbing against the ring member 60, the progress of wear due to continuous rubbing is reduced or prevented.
Since the ring member 60 can move in the axial direction within the gap in the state shown in FIG. 8, the fixing belt 6A1 is displaced when the pressure roller 6B1 is in contact with the fixing belt 6A1 and rotates when the paper is passed. Can move freely in the axial direction.
In this state, the positional relationship between the ring member 60 and the fixing belt 6A1 maintains the positional relationship determined when the opening / closing cover 100B is opened. As a result, even when the fixing belt 6A1 starts rotating again, collision with the support flange portion 50 due to the offset of the fixing belt 6A1 is avoided, and furthermore, constant contact with the ring member 60 is avoided. As a result, cracks and breakage on one surface of the end portion in the width direction of the fixing belt 6A1 are reduced or prevented, and progress of wear on the end surface in the width direction is reduced.

In the above configuration, the force that hinders the movement of the fixing belt 6A1 in the width direction when the pressure roller 6B1 is separated from the fixing belt 6A1 is removed, and the fixing belt 6A1 is positioned via the positioning of the ring member 60 with respect to the support flange portion 50. Is positioned at the specified position.
The ring member 60 prevents the surface of the end portion in the width direction of the fixing belt 6A1 from directly striking against the end surface of the boss portion 50A of the support flange portion, and weakens the reaction force to the fixing belt 6A1 generated from the striking force. Therefore, cracks and breakage in the fixing belt 6A1 can be reduced.
Moreover, since the ring member 60 contacts and moves when the fixing belt 6A1 is offset, the fixing belt 6A1 does not always contact the surface of the end portion in the width direction. As a result, it is possible to reduce or prevent the wear at the end of the fixing belt 6A1 in the width direction from advancing the wear over time due to the contact with the support flange 50 at all times.
As a result, mechanical deterioration due to wear, cracks or breakage can be prevented, and even if a fixing belt having low strength is used, it is possible to extend the service life.

  Another example of the ring member 60 is not limited to a member independent of the fixing belt 6A1, but is used as a member that can rotate integrally with the fixing belt 6A1 so as to face the end in the width direction of the fixing belt 6A1. It is also possible. In this case, it is preferable that the ring member 60 has a surface facing the boss portion 50A formed of a low friction coefficient material in order to reduce movement resistance when moving together with the fixing belt 6A1.

As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to this specific embodiment, Unless it is specifically limited by the above-mentioned description, this invention described in the claim is described. Various modifications and changes are possible within the scope of the gist of the invention.
The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

6 fixing device 6A1 fixing belt 6A3 nip forming member 6B1 counter rotating member 50 support flange portion 60 ring member 70 movable positioning mechanism 71 guide member 80 contacting / separating mechanism 81 lever member 90, 92 cam 100 image forming apparatus 100B opening / closing member P nip portion

JP 2004-286922 A Japanese Patent No. 2861280 JP 2010-66583 A JP 2003-295649 A

Claims (8)

A rotatable endless fixing belt;
An opposing rotating body that forms a nip portion with the fixing belt in a contact state in contact with the fixing belt;
A ring member facing the end in the width direction of the fixing belt and rotatable integrally with the fixing belt;
A support flange portion that forms a gap larger than the thickness of the ring member between the end portion in the width direction in a state where the fixing belt occupies a specified position in the width direction;
And a movable positioning mechanism that positions the end portion in the width direction by positioning the ring member with respect to the support flange portion in the width direction and positions the fixing belt at the specified position. A contact / separation mechanism for contacting / separating the fixing belt and the counter rotating body;
The movable positioning mechanism includes a guide member that advances and retreats between the support flange portion and the ring member in the width direction, and the fixing belt and the counter rotating body are separated from each other by the contact / separation mechanism. The fixing device according to claim 1, wherein the fixing belt is positioned at the specified position by causing the guide member to enter between the support flange portion and the ring member in the width direction. The contact / separation mechanism has a cam that contacts and separates the counter rotating body and the fixing belt by rotation,
The movable positioning mechanism causes the guide member to enter between the support flange portion and the ring member in the width direction in conjunction with the posture of the cam when the separated state is formed by rotation of the cam. The fixing device according to claim 2, further comprising a lever member.   The thickness of the guide member in the width direction is set to a thickness in which the fixing belt occupies the specified position in a state where the end surfaces of the guide member in the width direction are in contact with the support flange portion and the ring member, respectively. The fixing device according to claim 1, wherein the fixing device is a fixing device. The fixing belt and the ring member are rotatable independently of each other;
The fixing device according to claim 1, wherein an end surface of the ring member that abuts on the end portion is made of a low friction coefficient material.   The fixing device according to claim 1, wherein the fixing belt and the ring member are integral and rotate integrally.   An image forming apparatus comprising the fixing device according to claim 1. Having an opening and closing member for opening and closing the inside of the image forming apparatus,
The image forming apparatus according to claim 7, wherein the counter rotating body is supported by the opening / closing member and contacts and separates from the fixing belt according to opening / closing of the opening / closing member.

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